Volumetric imaging of optically cleared and fluorescently labeled animal tissue (VIOLA) for quantifying the 3D biodistribution of nanoparticles at cellular resolution in tumor tissue.

Nanoparticle (NP) technology holds significant promise to mediate targeted drug delivery to specific organs in the body. Understanding the 3D biodistribution of NPs in heterogeneous environments such as the tumor tissue can provide crucial information on efficacy, safety and potential clinical outcomes. Here we present a novel end-to-end workflow, VIOLA, which makes use of tissue clearing methodology in conjunction with high resolution imaging and advanced 3D image processing to quantify the spatiotemporal 3D biodistribution of fluorescently labeled ACCURIN® NPs. Specifically, we investigate the spatiotemporal biodistribution of NPs in three different murine tumor models (CT26, EMT6, and KPC-GEM) of increasing complexity and translational relevance. We have developed new endpoints to characterize NP biodistribution at multiple length scales. Our observations reveal that the macroscale NP biodistribution is spatially heterogeneous and exhibits a gradient with relatively high accumulation at the tumor periphery that progressively decreases towards the tumor core in all the tumor models. Microscale analysis revealed that NP extravasation from blood vessels increases in a time dependent manner and plateaus at 72 h post injection. Volumetric analysis and pharmacokinetic modeling of NP biodistribution in the vicinity of the blood vessels revealed that the local NP density exhibits a distance dependent spatiotemporal biodistribution which provide insights into the dynamics of NP extravasation in the tumor tissue. Our data represents a comprehensive analysis of NP biodistribution at multiple length scales in different tumor models providing unique insights into their spatiotemporal dynamics. Specifically, our results show that NPs exhibit a dynamic equilibrium with macroscale heterogeneity combined with microscale homogeneity.

Behavioral, Histopathologic, and Molecular Biological Responses of Nanoparticle- and Solution-Based Formulations of Vincristine in Mice.

Clinical use of the chemotherapeutic agent vincristine (VCR) is limited by chemotherapy-induced peripheral neuropathy (CiPN). A new formulation of VCR encapsulated by nanoparticles has been proposed and developed to alleviate CiPN. We hypothesized in nonclinical animals that the nanoparticle drug would be less neurotoxic due to different absorption and distribution properties to the peripheral nerve from the unencapsulated free drug. Here, we assessed whether VCR encapsulation in nanoparticles alleviates CiPN using behavioral gait analysis (CatWalk), histopathologic and molecular biological (RT-qPCR) approaches. Adult male C57BL/6 mice were assigned to 3 groups (empty nanoparticle, nano-VCR, solution-based VCR, each n = 8). After 15 days of dosing, animals were euthanized for tissue collection. It was shown that intraperitoneal administration of nano-VCR (0.15 mg/kg, every other day) and the empty nanoparticle resulted in no changes in gait parameters; whereas, injection of solution-based VCR resulted in decreased run speed and increased step cycle and stance (P < 0.05). There were no differences in incidence and severity of degeneration in the sciatic nerves between the nano-VCR-dosed and solution-based VCR-dosed animals. Likewise, decreased levels of a nervous tissue-enriched microRNA-183 in circulating blood did not show a significant difference between the nano- and solution-based VCR groups (P > 0.05). Empty nanoparticle administration did not cause any behavioral, microRNA, or structural changes. In conclusion, this study suggests that the nano-VCR formulation may alleviate behavioral changes in CiPN, but it does not improve the structural changes of CiPN in peripheral nerve. Nanoparticle properties may need to be optimized to improve biological observations.

A novel in situ hydrophobic ion paring (HIP) formulation strategy for clinical product selection of a nanoparticle drug delivery system.

The present studies were aimed at formulating AZD2811-loaded polylactic acid-polyethylene glycol (PLA-PEG) nanoparticles with adjustable release rates without altering the chemical structures of the polymer or active pharmaceutical ingredient (API). This was accomplished through the use of a hydrophobic ion pairing approach. A series of AZD2811-containing nanoparticles with a variety of hydrophobic counterions including oleic acid, 1-hydroxy-2-naphthoic acid, cholic acid, deoxycholic acid, dioctylsulfosuccinic acid, and pamoic acid is described. The hydrophobicity of AZD2811 was increased through formation of ion pairs with these hydrophobic counterions, producing nanoparticles with exceptionally high drug loading-up to five fold higher encapsulation efficiency and drug loading compared to nanoparticles made without hydrophobic ion pairs. Furthermore, the rate at which the drug was released from the nanoparticles could be controlled by employing counterions with various hydrophobicities and structures, resulting in release half-lives ranging from about 2 to 120h using the same polymer, nanoparticle size, and nanoemulsion process. Process recipe variables affecting drug load and release rate were identified, including pH and molarity of quench buffer. Ion pair formation between AZD2811 and pamoic acid as a model counterion was investigated using solubility enhancement as well as nuclear magnetic resonance spectroscopy to demonstrate solution-state interactions. Further evidence for an ion pairing mechanism of controlled release was provided through the measurement of API and counterion release profiles using high-performance liquid chromatography, which had stoichiometric relationships. Finally, Raman spectra of an AZD2811-pamoate salt compared well with those of the formulated nanoparticles, while single components (AZD2811, pamoic acid) alone did not. A library of AZD2811 batches was created for analytical and preclinical characterization. Dramatically improved preclinical efficacy and tolerability data were generated for the pamoic acid lead formulation, which has been selected for evaluation in a Phase 1 clinical trial (ClinicalTrials.gov Identifier NCT 02579226). This work clearly demonstrates the importance of assessing a wide range of drug release rates during formulation screening as a critical step for new drug product development, and how utilizing hydrophobic ion pairing enabled this promising nanoparticle formulation to proceed into clinical development.

Establishment and genomic characterization of mouse xenografts of human primary prostate tumors.

Serum prostate-specific antigen screening has led to earlier detection and surgical treatment of prostate cancer, favoring an increasing incidence-to-mortality ratio. However, about one third of tumors that are diagnosed when still confined to the prostate can relapse within 10 years from the first treatment. The challenge is therefore to identify prognostic markers of aggressive versus indolent tumors. Although several preclinical models of advanced prostate tumors are available, a model that recapitulates the genetic and growth behavior of primary tumors is still lacking. Here, we report a complete histopathological and genomic characterization of xenografts derived from primary localized low- and high-grade human prostate tumors that were implanted under the renal capsule of immunodeficient mice. We obtained a tumor take of 56% and show that these xenografts maintained the histological as well as most genomic features of the parental tumors. Serum prostate-specific antigen levels were measurable only in tumor xenograft-bearing mice, but not in those implanted with either normal prostate tissue or in tumors that likely regressed. Finally, we show that a high proliferation rate, but not the pathological stage or the Gleason grade of the original tumor, was a fundamental prerequisite for tumor take in mice. This mouse xenograft model represents a useful preclinical model of primary prostate tumors for their biological characterization, biomarker discovery, and drug testing.

Fatty acid synthase: a metabolic enzyme and candidate oncogene in prostate cancer.

BACKGROUND: Overexpression of the fatty acid synthase (FASN) gene has been implicated in prostate carcinogenesis. We sought to directly assess the oncogenic potential of FASN. METHODS: We used immortalized human prostate epithelial cells (iPrECs), androgen receptor-overexpressing iPrECs (AR-iPrEC), and human prostate adenocarcinoma LNCaP cells that stably overexpressed FASN for cell proliferation assays, soft agar assays, and tests of tumor formation in immunodeficient mice. Transgenic mice expressing FASN in the prostate were generated to assess the effects of FASN on prostate histology. Apoptosis was evaluated by Hoechst 33342 staining and by fluorescence-activated cell sorting in iPrEC-FASN cells treated with stimulators of the intrinsic and extrinsic pathways of apoptosis (ie, camptothecin and anti-Fas antibody, respectively) or with a small interfering RNA (siRNA) targeting FASN. FASN expression was compared with the apoptotic index assessed by the terminal deoxynucleotidyltransferase-mediated UTP end-labeling method in 745 human prostate cancer samples by using the least squares means procedure. All statistical tests were two-sided. RESULTS: Forced expression of FASN in iPrECs, AR-iPrECs, and LNCaP cells increased cell proliferation and soft agar growth. iPrECs that expressed both FASN and androgen receptor (AR) formed invasive adenocarcinomas in immunodeficient mice (12 of 14 mice injected formed tumors vs 0 of 14 mice injected with AR-iPrEC expressing empty vector (P < .001, Fisher exact test); however, iPrECs that expressed only FASN did not. Transgenic expression of FASN in mice resulted in prostate intraepithelial neoplasia, the incidence of which increased from 10% in 8- to 16-week-old mice to 44% in mice aged 7 months or more (P = .0028, Fisher exact test), but not in invasive tumors. In LNCaP cells, siRNA-mediated silencing of FASN resulted in apoptosis. FASN overexpression protected iPrECs from apoptosis induced by camptothecin but did not protect iPrECs from Fas receptor-induced apoptosis. In human prostate cancer specimens, FASN expression was inversely associated with the apoptotic rate (mean percentage of apoptotic cells, lowest vs highest quartile of FASN expression: 2.76 vs 1.34, difference = 1.41, 95% confidence interval = 0.45 to 2.39, Ptrend = .0046). CONCLUSIONS: These observations suggest that FASN can act as a prostate cancer oncogene in the presence of AR and that FASN exerts its oncogenic effect by inhibiting the intrinsic pathway of apoptosis.

BRAF activation initiates but does not maintain invasive prostate adenocarcinoma.

Prostate cancer is the second leading cause of cancer-related deaths in men. Activation of MAP kinase signaling pathway has been implicated in advanced and androgen-independent prostate cancers, although formal genetic proof has been lacking. In the course of modeling malignant melanoma in a tyrosinase promoter transgenic system, we developed a genetically-engineered mouse (GEM) model of invasive prostate cancers, whereby an activating mutation of BRAF(V600E)--a mutation found in approximately 10% of human prostate tumors--was targeted to the epithelial compartment of the prostate gland on the background of Ink4a/Arf deficiency. These GEM mice developed prostate gland hyperplasia with progression to rapidly growing invasive adenocarcinoma without evidence of AKT activation, providing genetic proof that activation of MAP kinase signaling is sufficient to drive prostate tumorigenesis. Importantly, genetic extinction of BRAF(V600E) in established prostate tumors did not lead to tumor regression, indicating that while sufficient to initiate development of invasive prostate adenocarcinoma, BRAF(V600E) is not required for its maintenance.

The oncogenic properties of mutant p110alpha and p110beta phosphatidylinositol 3-kinases in human mammary epithelial cells.

The PIK3CA gene encoding the p110alpha subunit of Class IA phosphatidylinositol 3-kinases (PI3Ks) is frequently mutated in human tumors. Mutations in the PIK3CB gene encoding p110beta, the only other widely expressed Class IA PI3K, have not been reported. We compared the biochemical activity and transforming potential of mutant forms of p110alpha and p110beta in a human mammary epithelial cell system. The two most common tumor-derived alleles of p110alpha, H1047R and E545K, potently activated PI3K signaling. Human mammary epithelial cells expressing these alleles grew efficiently in soft agar and as orthotopic tumors in nude mice. We also examined a third class of mutations in p110alpha, those in the p85-binding domain. A representative tumor-derived p85-binding-domain mutant R38H showed modestly reduced p85 binding and weakly activated PI3K/Akt signaling. In contrast, a deletion mutant lacking the entire p85-binding domain efficiently activated PI3K signaling. When we constructed in p110beta a mutation homologous to the E545K allele of p110alpha, the resulting p110beta mutant was only weakly activated and allowed minimal soft-agar growth. However, a gene fusion of p110beta with the membrane anchor from c-Src was highly active and transforming in both soft-agar and orthotopic nude mouse assays. Thus, although introduction of activating mutations from p110alpha at the corresponding sites in p110beta failed to render the enzyme oncogenic in human cells, the possibility remains that other mutations might activate the beta isoform.

Modulation of epithelial neoplasia and lymphoid hyperplasia in PTEN+/- mice by the p85 regulatory subunits of phosphoinositide 3-kinase.

Mice with heterozygous deletion of the PTEN tumor suppressor gene develop a range of epithelial neoplasia as well as lymphoid hyperplasia. Previous studies suggest that PTEN suppresses tumor formation by acting as a phosphoinositide phosphatase to limit signaling by phosphoinositide 3-kinase (PI3K). Here, we examined the effect of deleting various regulatory subunits of PI3K (p85alpha and p85beta) on epithelial neoplasia and lymphoid hyperplasia in PTEN+/- mice. Interestingly, we found the loss of one p85alpha allele with or without the loss of p85beta led to increased incidence of intestinal polyps. Signaling downstream of PI3K was enhanced in the PTEN+/-p85alpha+/-p85beta-/- polyps, as judged by an increased fraction of both cells with cytoplasmic staining of the transcription factor FKHR and cells with positive staining for the proliferation marker Ki-67. In contrast, the incidence of prostate intraepithelial neoplasia was not significantly altered in PTEN+/- mice heterozygous for p85alpha or null for p85beta, whereas the fraction of proliferating cells in prostate intraepithelial neoplasia was reduced in mice lacking p85beta. Finally, there was no significant change in T lymphocyte hyperplasia in the PTEN+/- mice with various p85 deletions, although anti-CD3-stimulated AKT activation was somewhat reduced in the p85alpha+/- background. These results indicate that decreasing the levels of different p85 regulatory subunits can result in enhanced PI3K signaling in some tissues and decreased PI3K signaling in others, supporting the model that, although p85 proteins are essential for class I(A) PI3K signaling, they can function as inhibitors of PI3K signaling in some tissues and thus suppress tumor formation.